# Period Filters 1.0

## Candidate Recommendation 28 March 2008

Copyright ©2008 XBRL International Inc., All Rights Reserved.

This version:
  <http://www.xbrl.org/Specification/periodFilters/CR-2008-03-28/periodFilters-CR-2008-03-28.html>
Editors:
  Phillip Engel, Morgan Stanley <phillip.engel@morganstanley.com>
  Herm Fischer, UBMatrix / Mark V Systems <fischer@markv.com>
  Victor Morilla, Banco de España <victor.morilla@bde.es>
  Jim Richards, JDR & Associates <jdrassoc@iinet.net.au>
  Geoff Shuetrim, Galexy <geoff@galexy.net>
  David vun Kannon, PricewaterhouseCoopers LLP <david.k.vunkannon@us.pwc.com>
  Hugh Wallis, XBRL International <hughwallis@xbrl.org>
Contributors:
  Cliff Binstock, Coyote Reporting <cliff.binstock@coyotereporting.com>
  Paul Bull, Morgan Stanley <paul.bull@morganstanley.com>
  Mark Goodhand, Decisionsoft <mrg@decisionsoft.com>
  Masatomo Goto, Fujitsu <mg@jp.fujitsu.com>
  Walter Hamscher, Standard Advantage / Consultant to PricewaterhouseCoopers LLP <walter@hamscher.com>
  Ignacio Hernández-Ros, Reporting Estandar S.L. <ignacio@hernandez-ros.com>
  Roland Hommes, Rhocon / Consultant to Netherlands Tax and Customs Administration <roland@rhocon.nl>
  Andy Harris, UBMatrix <andy.harris@ubmatrix.com>
  Pablo Navarro Salvador, Atos Origin sae <pablo.navarro@atosorigin.com>
  Michele Romanelli, Banca d'Italia <michele.romanelli@bancaditalia.it>
  Chris Simmons, DecisionSoft <cps@decisionsoft.com>
  Masaru Uchida, Fujitsu <m-uchida@jp.fujitsu.com>
  Hitoshi Okumura, Fujitsu <okmr@jp.fujitsu.com>
  Takahide Muramoto, Fujitsu <taka.muramoto@jp.fujitsu.com>

## Status

Circulation of this Candidate Recommendation is unrestricted. This document is normative. Other documents may supersede this document. Recipients are invited to submit comments to formula-feedback@xbrl.org, and to submit notification of any relevant patent rights of which they are aware and to provide supporting documentation.

## Abstract

This specification is an extension to the XBRL Variables Specification [VARIABLES]. It defines syntax for filters that condition upon the features of the period at which or over which facts have been measured.

# 1 Introduction

This specification is an extension to the XBRL Variables Specification [VARIABLES]. It defines syntax for filters that condition upon the features of the period at which or over which facts have been measured.

All of the filters defined in this specification can cover the period aspect.

## 1.1 Background

This specification is a member of a suite of similar specifications that define specific types of criteria that can be used to select facts from XBRL instances. It enhances the fact selection capabilities of the XBRL Variables Specification [VARIABLES].

## 1.2 Relationship to other work

This specification depends upon the XBRL Specification [XBRL 2.1], the XBRL Variables Specification [VARIABLES]. In the event of any conflicts between this specification and the specifications upon which it depends, this specification does not prevail.

## 1.3 Language independence

The official language of XBRL International's own work products is English and the preferred spelling convention is UK English.

## 1.4 Terminology

This specification is consistent with the definitions of any of the terms defined in specifications that it depends on.

## 1.5 Document conventions (non-normative)

Documentation conventions follow those set out in the XBRL Variables Specification [VARIABLES].

## 1.6 Namespaces and namespace prefixes

Namespace prefixes [XML NAMES] will be used for elements and attributes in the form `ns:name` where `ns` is the namespace prefix and `name` is the local name. Throughout this specification, the mappings from namespace prefixes to actual namespaces is consistent with Table 1.

The prefix column in Table 1 is non normative. The namespace URI column is normative.

Table 1: Namespaces and namespace prefixes

Prefix | Namespace URI
--- | ---
`pf` | `http://xbrl.org/2008/filter/period`
`xbrlpfe` | `http://xbrl.org/2008/filter/period/error`
`eg` | `http://example.com/`
`fn` | `http://www.w3.org/2005/xpath-functions`
`link` | `http://www.xbrl.org/2003/linkbase`
`xbrli` | `http://www.xbrl.org/2003/instance`
`xfi` | `http://www.xbrl.org/2005/function/instance`
`xbrldi` | `http://xbrl.org/2006/xbrldi`
`xbrldt` | `http://xbrl.org/2005/xbrldt`
`xl` | `http://www.xbrl.org/2003/XLink`
`xlink` | `http://www.w3.org/1999/xlink`
`xs` | `http://www.w3.org/2001/XMLSchema`
`xsi` | `http://www.w3.org/2001/XMLSchema-instance`
`gen` | `http://xbrl.org/2008/generic`
`variable` | `http://xbrl.org/2008/variable`
`iso4217` | `http://www.xbrl.org/2003/iso4217`

## 1.7 XPath usage

XPath usage is identical to that in the XBRL Variables Specification [VARIABLES].

# 2 Syntax

This specification only provides a textual declaration of syntax constraints when those constraints are not expressed by the normative schema supplied with this specification.

Explanations of elements and attributes are only supplied when explanations are not already provided in other specifications.

Unless explicitly stated otherwise, a reference to a specific element MUST be read as a reference to that element or to any element in its substitution group.

## 2.1 Period filter

A period filter is declared by a `<pf:period>` element.

The syntax for the `<pf:period>` element is defined by the normative schema supplied with this specification.

The period filter can be used to match facts based upon a broad range of criteria relating to the period over which or at which they have been measured.

The XPath expression implied by a period filter is:

`xfi:period(.)[#test]`

where `#test` is the value of the `@test` attribute on the period filter.

Example 1: Period filters

`@test` attribute value | Implied constraint
--- | ---
`xfi:period-start(.) eq xfi:period-end(xfi:period($eg:other))` | The fact must have a duration period that starts at the same instant as the end of the duration period of the fact that the variable `eg:other` has evaluated to.

## 2.2 Period-start filter

A period-start filter is declared by a `<pf:periodStart>` element.

The syntax for the `<pf:periodStart>` element is defined by the normative schema supplied with this specification.

The period-start filter can be used to match facts based upon the start of the duration over which they have been measured.

If the period-start filter has a `@time` attribute, then the XPath expression implied by a period-start filter is:

`xfi:period(.)[ if (xfi:is-start-end-period(.)) then (xfi:period-start(.) eq fn:dateTime(xs:date('#date'), xs:time('#time'))) else fn:false() ]`

where `#date` is the value of the `@date` attribute on the period-start filter and `#time` is the value of the `@time` attribute on the period-start filter.

If the period-start filter does not have a `@time` attribute, then the XPath expression implied by a period-start filter is:

`xfi:period(.)[ if (xfi:is-start-end-period(.)) then (xfi:period-start(.) eq fn:dateTime(xs:date('#date'), xs:time('00:00:00'))) else fn:false() ]`

where `#date` is the value of the `@date` attribute on the period-start filter.

Example 2: Period-start filters

`@date` attribute value | `@time` attribute value | Implied constraint
--- | --- | ---
`2006-01-01` | `omitted` | Facts must be reported with a finite duration that begins at the start of the day on January 1, 2006. See the relevant section of the XBRL Specification for a more detailed explanation.
`2007-01-01` | `00:00:00` | Facts must be reported with a finite duration that begins at the start of the day on January 1, 2007.

## 2.3 Period-end filter

A period-end filter is declared by a `<pf:periodEnd>` element.

The syntax for the `<pf:periodEnd>` element is defined by the normative schema supplied with this specification.

The period-end filter can be used to match facts based upon the end of the duration over which they have been measured.

If the period-end filter has a `@time` attribute, then the XPath expression implied by a period-end filter is:

`xfi:period(.)[ if (xfi:is-start-end-period(.)) then (xfi:period-end(.) eq fn:dateTime(xs:date('#date'), xs:time('#time'))) else fn:false() ]`

where `#date` is the value of the `@date` attribute on the period-end filter and `#time` is the value of the `@time` attribute on the period-end filter.

If the period-end filter does not have a `@time` attribute, then the XPath expression implied by a period-end filter is:

`xfi:period(.)[ if (xfi:is-start-end-period(.)) then (xfi:period-end(.) eq (fn:dateTime(xs:date('#date'), xs:time('00:00:00'))+ xs:dayTimeDuration('P1D'))) else fn:false() ]`

where `#date` is the value of the `@date` attribute on the period-end filter.

Example 3: Period-end filters

`@date` attribute value | `@time` attribute value | Implied constraint
--- | --- | ---
`2006-01-01` | `omitted` | Facts must be reported with a finite duration that ends at the end of the day on January 1, 2006.
`2007-01-01` | `00:00:00` | Facts must be reported with a finite duration that ends at the start of the day on January 1, 2007.

## 2.4 Period-instant filter

A period-instant filter is declared by a `<pf:periodInstant>` element.

The syntax for the `<pf:periodInstant>` element is defined by the normative schema supplied with this specification.

The period-instant filter can be used to match facts based upon the instant at which they have been measured.

If the period-instant filter has a `@time` attribute, then the XPath expression implied by a period-instant filter is:

`xfi:period(.)[ if (xfi:is-instant-period(.)) then (xfi:instant(.) eq fn:dateTime(xs:date('#date'), xs:time('#time'))) else fn:false() ]`

where `#date` is the value of the `@date` attribute on the period-instant filter and `#time` is the value of the `@time` attribute on the period-instant filter.

If the period-instant filter does not have a `@time` attribute, then the XPath expression implied by a period-instant filter is:

`xfi:period(.)[ if (xfi:is-instant-period(.)) then (xfi:instant(.) eq (fn:dateTime(xs:date('#date'), xs:time('00:00:00'))+ xs:dayTimeDuration('P1D'))) else fn:false() ]`

where `#date` is the value of the `@date` attribute on the period-instant filter.

Example 4: Period-instant filters

`@date` attribute value | `@time` attribute value | Implied constraint
--- | --- | ---
`2006-01-01` | `omitted` | Facts must be reported as at the end of January 1, 2006.
`2007-01-01` | `00:00:00` | Facts must be reported as at the start of January 1, 2007.

## 2.5 Forever filter

A forever filter is declared by a `<pf:forever>` element.

The syntax for the `<pf:forever>` element is defined by the normative schema supplied with this specification.

The forever filter can be used to match facts that are reported with a forever period.

The XPath expression implied by a forever filter is:

`xfi:period(.)[xfi:is-forever-period(.)]`

## 2.6 Instant-duration filter

A instant-duration filter is declared by an `<pf:instantDuration>` element.

The syntax for the `<pf:instantDuration>` element is defined by the normative schema supplied with this specification.

The instant-duration filter can be used to match facts that are reported as at an instant where that instant matches the start or end of the duration for which another fact has been reported.

If the `@boundary` attribute equals `start` then the XPath expression implied by an instant-duration filter is:

`xfi:period(.)[ if (xfi:is-instant-period(.) and xfi:is-start-end-period(xfi:period($#variable))) then (xfi:instant(.) eq xfi:period-start(xfi:period($#variable))) else fn:false() ]`

where `#variable` is the QName contained by the `@variable` attribute on the instant-duration filter.

If the `@boundary` attribute equals `end` then the XPath expression implied by an instant-duration filter is:

`xfi:period(.)[ if (xfi:is-instant-period(.) and xfi:is-start-end-period(xfi:period($#variable))) then (xfi:instant(.) eq xfi:period-end(xfi:period($#variable))) else fn:false() ]`

where `#variable` is the QName contained by the `@variable` attribute on the instant-duration filter.

Example 5: Instant-duration filters

`@boundary` attribute value | `@variable` attribute value | Implied constraint
--- | --- | ---
`start` | `eg:variableA` | Facts must be reported for instants that are equal to the start of the duration of the fact that variable `eg:variableA` has evaluated to.

# Appendix A Normative schema

The following is the XML schema provided as part of this specification. This is normative. Non-normative versions (which should be identical to these except for appropriate comments indicating their non-normative status) are also provided as separate files for convenience of users of the specification.

NOTE: (non-normative) Following the schema maintenance policy of XBRL International, it is the intent (but is not guaranteed) that the location of non-normative versions of these schemas on the web will be as follows:

1. While any schema is the most current RECOMMENDED version and until it is superseded by any additional errata corrections a non-normative version will reside on the web in the directory `http://www.xbrl.org/2008/` - during the drafting process for this specification this directory should contain a copy of the most recent published version of the schema at http://www.xbrl.org/2008/period-filter.xsd.
2. A non-normative version of each schema as corrected by any update to the RECOMMENDATION will be archived in perpetuity on the web in a directory that will contain a unique identification indicating the date of the update.

<schema xmlns:pf="http://xbrl.org/2008/filter/period" xmlns:variable="http://xbrl.org/2008/variable" xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://xbrl.org/2008/filter/period" elementFormDefault="qualified">
<import namespace="http://www.xbrl.org/2003/XLink" schemaLocation="http://www.xbrl.org/2003/xl-2003-12-31.xsd"/>
<import namespace="http://xbrl.org/2008/variable" schemaLocation="variable.xsd"/>
<element id="xml-period-filter" name="period" substitutionGroup="variable:filter">
<complexType mixed="true">
<complexContent mixed="true">
<extension base="variable:resource.type">
<attribute name="test" type="variable:expression" use="required"/>
</extension>
</complexContent>
</complexType>
</element>
<complexType name="date-time.model" mixed="true">
<complexContent mixed="true">
<extension base="variable:resource.type">
<attribute name="date" type="variable:expression" use="required"/>
<attribute name="time" type="variable:expression" use="optional"/>
</extension>
</complexContent>
</complexType>
<element id="xml-period-start-filter" name="periodStart" type="pf:date-time.model" substitutionGroup="variable:filter"/>
<element id="xml-period-end-filter" name="periodEnd" type="pf:date-time.model" substitutionGroup="variable:filter"/>
<element id="xml-period-instant-filter" name="periodInstant" type="pf:date-time.model" substitutionGroup="variable:filter"/>
<element id="xml-forever-filter" name="forever" substitutionGroup="variable:filter" type="variable:resource.type"/>
<element id="xml-instant-duration-filter" name="instantDuration" substitutionGroup="variable:filter">
<complexType mixed="true">
<complexContent mixed="true">
<extension base="variable:resource.type">
<attribute name="variable" type="QName" use="required"/>
<attribute name="boundary" use="required">
<simpleType>
<restriction base="token">
<enumeration value="start"/>
<enumeration value="end"/>
</restriction>
</simpleType>
</attribute>
</extension>
</complexContent>
</complexType>
</element>
</schema>

# Appendix B References

VARIABLES
  XBRL International Inc.. "XBRL Variables 1.0, Public Working Draft"
  Phillip Engel, Herm Fischer, Victor Morilla, Jim Richards, Geoff Shuetrim, David vun Kannon, and Hugh Wallis.
  (See ../../variables/CR-2008-03-28/variables-CR-2008-03-28.html)
XBRL 2.1
  XBRL International Inc.. "Extensible Business Reporting Language (XBRL) 2.1"
  Phillip Engel, Walter Hamscher, Geoff Shuetrim, David vun Kannon, and Hugh Wallis.
  (See http://www.xbrl.org/Specification/XBRL-RECOMMENDATION-2003-12-31+Corrected-Errata-2006-12-18.htm)
XML NAMES
  W3C (World Wide Web Consortium). "Namespaces in XML 1.0 (Second Edition)"
  Tim Bray, Dave Hollander, Andrew Layman, and Richard Tobin.
  (See http://www.w3.org/TR/REC-xml-names/)
XML SCHEMA STRUCTURES
  W3C (World Wide Web Consortium). "XML Schema Part 1: Structures Second Edition"
  Henry S. Thompson, David Beech, Murray Maloney, and Noah Mendelsohn.
  (See http://www.w3.org/TR/xmlschema-1/)

# Appendix C Intellectual property status (non-normative)

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to XBRL International or XBRL organizations, except as required to translate it into languages other than English. Members of XBRL International agree to grant certain licenses under the XBRL International Intellectual Property Policy (www.xbrl.org/legal).

This document and the information contained herein is provided on an "AS IS" basis and XBRL INTERNATIONAL DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

The attention of users of this document is directed to the possibility that compliance with or adoption of XBRL International specifications may require use of an invention covered by patent rights. XBRL International shall not be responsible for identifying patents for which a license may be required by any XBRL International specification, or for conducting legal inquiries into the legal validity or scope of those patents that are brought to its attention. XBRL International specifications are prospective and advisory only. Prospective users are responsible for protecting themselves against liability for infringement of patents. XBRL International takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Members of XBRL International agree to grant certain licenses under the XBRL International Intellectual Property Policy (www.xbrl.org/legal).

# Appendix D Acknowledgements (non-normative)

This document could not have been written without the contributions of many people including the participants in the Formula Working Group.

# Appendix E Document history (non-normative)

Date | Author | Details
--- | --- | ---
18 December 2006 | Geoff Shuetrim | First internal working draft created, drawing extensively on the previous formula specification drafts.
25 April 2007 | Geoff Shuetrim | Changed the target namespace of the normative schema.
30 April 2007 | Geoff Shuetrim | Significant redesign of the period filters, broadening the usefulness of the period filter and enhancing the flexibility of the specific period filters. Added a matching period filter that is specifically intended to match one period to another. Added an instant-duration filter specifically designed to simplify the declaration of period relationships between instant and duration concepts. In relation to implicit filtering, added indication that all of the filters defined in this specification cover the period aspect.
08 May 2007 | Geoff Shuetrim | Added clarification about the fact aspect covered by the filters defined in this specification.
29 May 2007 | Geoff Shuetrim | Changed the target namespace of the normative schema again. Fixed incorrect reference to an instant filter in the description of the period filter.
11 June 2007 | Geoff Shuetrim | Fixed the XML Schema to make the time attributes optional, reflecting the wording of the specification. Clarified the example that goes with the instant-duration period filter.
24 July 2007 | Hugh Wallis | Edited for public working draft publication.
06 November 2007 | Geoff Shuetrim | Converted the specification to XML format. Added in the definitions and the hyperlinks to the relevant sections of the normative schema. Removed the period match filter that will be moved to the match filters specification that will support relative and implicit filtering. Added examples to each of the filters. Modified the design of the instant-duration filter to reduce the need for complex XPath structures in the filter customisation.
07 November 2007 | Geoff Shuetrim | Added the forever filter as suggested by Ken Layton.
26 November 2007 | Jim Richards | Replaced "an" with "a" in a number of definitions.
18 December 2007 | Geoff Shuetrim | Removed comments.
24 January 2008 | Geoff Shuetrim | Changed location of hyperlinks to fragments of the the normative schema.
31 January 2008 | Geoff Shuetrim | Made the date.time.model have mixed content as suggested by Masatomo Goto Changed `xs:dateTime()` function calls in the implied XPath expressions to `fn:dateTime()` function calls as suggested by Masatomo Goto
01 February 2008 | Geoff Shuetrim | Fixed up the examples for the period-instant filter as suggested by Masatomo Goto, also including a reference to the relevant section of the XBRL specification for interpreting instants that are reported with date but not time information.
05 February 2008 | Geoff Shuetrim | Changed the XPath expressions to test that the period types are right before retrieving period values to ensure that errors are not being thrown by retrieving the wrong kinds of period values from a period when filtering and thus stopping the whole filtering process when the filter is just intended to reject such facts and continue.
08 February 2008 | Geoff Shuetrim | Fixed the incorrect name for the `xfi:period` function call. Fixed the duplicate `then` in various implied XPath expressions. Changed `xfi:period[ ]` to `xfi:period(.)[ ]`. Added the missing `xfi:period` function calls to the implied XPath expressions as required to access the period of facts that other variables have bound to. These mistakes were identified by Masatomo Goto.
12 February 2008 | Geoff Shuetrim | Converted remaining general equality tests to value equality tests in the implied XPath expressions.

# Appendix F Errata corrections in this document

This appendix contains a list of the errata that have been incorporated into this document. This represents all those errata corrections that have been approved by the XBRL International Formula Working Group up to and including 28 March 2008. Hyperlinks to relevant e-mail threads may only be followed by those who have access to the relevant mailing lists. Access to internal XBRL mailing lists is restricted to members of XBRL International Inc.

No errata have been incorporated into this document.